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With its 2007 report declaring that the "warming of the climate system is unequivocal," the U.N. Intergovernmental Panel on Climate Change won a Nobel Prize -- and a new degree of public trust in the controversial science of global warming.

But recent revelations about flaws in that seminal report, ranging from typos in key dates to sloppy sourcing, are undermining confidence not only in the panel's work but also in projections about climate change. Scientists who have pointed out problems in the report say the panel's methods and mistakes -- including admitting Saturday that it had overstated how much of the Netherlands was below sea level -- give doubters an opening.

It wasn't the first one. There is still a scientific consensus that humans are causing climate change. But in the past year, a cache of stolen e-mails, revealing that prominent climate scientists sought to prevent the publication of works by their detractors, has sullied their image as impartial academics. The errors in the U.N. report -- a document intended to be the last nail in the coffin of climate doubt -- are a serious problem that could end up forcing environmentalists to focus more on the old question of proving that climate change is a threat, instead of the new question of how to stop it.

Two Republican senators who have long opposed a cap on carbon emissions, James M. Inhofe (Okla.) and John Barrasso (Wyo.), are citing the errors as further reasons to block mandatory limits on greenhouse gas emissions. Last week, Barrasso called for an independent probe into the IPCC, suggesting that the United States should halt any action on climate until it verifies the panel's scientific conclusions.

Inhofe said Thursday in the Senate that the Environmental Protection Agency's efforts to curb greenhouse gases should be reexamined, since the U.N. panel's conclusions influenced the agency's finding that climate change poses a public threat. "The ramifications of the IPCC spread far and wide, most notably to the Environmental Protection Agency's finding that greenhouse gases from mobile sources endanger public health and welfare," Inhofe said. On Friday, a coalition of conservative groups filed a petition to overturn the EPA's finding on the same grounds.

"There is a sense that something's rotten in the state of the IPCC," said Richard H. Moss, a senior scientist at the Joint Global Change Research Institute at the University of Maryland, who has worked with the panel since 1993. "It's just wildly exaggerated. But we need to take a look and see if something needs to be improved."

The IPCC climate assessments are, by any standard, a massive undertaking. Thousands of scientists across the globe volunteer to evaluate tens of thousands of academic documents and translate them into plain-English reports that policymakers can understand.

Climate researchers say the errors do not disprove the U.N. panel's central conclusion: Climate change is happening, and humans are causing it. Some researchers said the U.N. panel's attitude -- appearing to promise that its results were infallible, and reacting slowly to evidence that they were not -- could undermine the rest of its work.

"What's happened here is that there's an industry of climate-change denialists who are trying to make it seem as though you can't trust anything that is between the covers" of the panel's report, said Jeffrey Kargel, a professor at the University of Arizona who studies glaciers. "It's really heartbreaking to see this happen, and to see that the IPCC left themselves open" to being attacked.

Kargel said he noticed an error in the report of the IPCC's second working group, a research unit, in 2007. The report said huge glaciers in the Himalayan mountains might disappear by 2035. Some glaciers are melting, but they are too enormous to disappear that quickly: "It's physically impossible to kill the ice that fast," Kargel said.

He said colleagues regarded the error as too ridiculous to fuss about until recently. Last month, the journal Science printed a letter to the editor that traced the origins of the mistaken data: The U.N. panel seemed to have quoted an activist group's report, not a peer-reviewed study. And, in citing another source, it appeared to have committed a serious typo: The year 2350 had become 2035.

Another line that has sparked scrutiny reads, "Up to 40 percent of the Amazonian forests could react drastically to even a slight reduction in precipitation," and links to a report co-written by the World Wildlife Fund. The analysis cited key work by Woods Hole Research Center senior scientist Daniel C. Nepstad, but the link to an advocacy group instead of a peer-reviewed paper infuriated conservatives.